The present invention relates to a method and apparatus for sensing the forces on a patellar implant in a human knee, and in particular to a method and apparatus for measuring the forces at the patellofemoral joint.
Advances in surgical technique, instrumentation and prosthesis design have enabled surgeons to achieve some satisfactory results in total knee arthroplasty. Advances have been made in the areas of tibial and femoral alignment and fixation such that the outcome of the femoral and tibial components of total knee arthroplasty has been excellent.
However, the patellofemoral component of total knee arthroplasty has been a source of problems and the patella remains a persistent cause of poor results. Little attention has been focused on the patella, and patellar implant complication is now one of the most frequent causes of total knee arthroplasty failure. Complications affecting the patellofemoral joint occur in up to ten percent of knee arthroplasties and account for up to fifty percent of revision knee procedures. Among the problems documented are postoperative patellar pain, fracture, loosening, subluxation, dislocation, and patellar implant wear.
A major cause of patellar implant complications has been identified as stress at the patellofemoral joint. It is therefore necessary to more accurately measure the forces that act on the patellar implant. While other methods have been used to attempt to measure patellar forces, there is a need for an apparatus which will enable direct measurement of all the forces acting on the patella at the patellofemoral joint.